Fenbufen

(BAN, USAN, rINN)
Fenbufen Chemical formula
Synonyms: CL-82204; Fenbufeeni; Fenbufén; Fenbufenas; Fenbufène; Fenbufenum. 4-(Biphenyl-4-yl)-4-oxobutyric acid.
Cyrillic synonym: Фенбуфен.

💊 Chemical information

Chemical formula: C16H14O3 = 254.3.
CAS — 36330-85-5.
ATC — M01AE05.
ATC Vet — QM01AE05.

Pharmacopoeias.

In Chin., Eur., and Jpn.

Ph. Eur. 6.2

(Fenbufen). A white or almost white, fine crystalline powder. Very slightly soluble in water; slightly soluble in alcohol, in acetone, and in dichloromethane.

💊 Adverse Effects, Treatment, and Precautions

As for NSAIDs in general, although the commonest adverse effects of fenbufen are skin rashes, usually occurring within the first 2 weeks of therapy, and particularly in women and in patients with seronegative rheumatoid arthritis or psoriatic arthritis. Disorders such as epidermal necrolysis, erythema multiforme, and Stevens-Johnson syndrome have also been reported. A small number of patients who develop rash may go on to develop a severe illness characterised by pulmonary eosinophilia or allergic alveolitis. Treatment with fenbufen should be stopped immediately if a rash appears.

Breast feeding.

UK licensed product information advises that fenbufen should be avoided in breast-feeding mothers, because of the presence of its metabolites in breast milk.

Effects on the blood.

Haemolytic anaemia1 and aplastic anaemia2 have been reported in patients receiving fenbufen.
1. Martland T, Stone WD. Haemolytic anaemia associated with fenbufen. BMJ 1988; 297: 921
2. Andrews R, Russell N. Aplastic anaemia associated with a nonsteroidal anti-inflammatory drug: relapse after exposure to another such drug. BMJ 1990; 301: 38.

Effects on the lungs.

In January 1989 the UK CSM reported that it had received 7 reports of a suspected association between rash and an allergic interstitial lung disorder in patients receiving fenbufen.1 In 5 patients, the lung disorder was diagnosed as pulmonary eosinophilia; in the 2 other patients the pulmonary component of the reaction was described as allergic alveolitis. Several of these reactions have been reported in the literature.2,3
1. CSM. Fenbufen, rash and pulmonary eosinophilia. Current Problems 24 1989. Also available at: http://www.mhra.gov.uk/ home/idcplg?IdcService=GET_FILE&dDocName= CON2024431&RevisionSelectionMethod=LatestReleased (accessed 01/11/07
2. Swinburn CR. Alveolitis and haemolytic anaemia induced by azapropazone. BMJ 1987; 294: 375
3. Burton GH. Rash and pulmonary eosinophilia associated with fenbufen. BMJ 1990; 300: 82–3.

Effects on the skin.

In September 1988 the UK CSM reported1that it was still receiving large numbers of reports of adverse reactions to fenbufen when such reports were expected to have declined. Fenbufen was the most commonly reported suspect drug in 1986 and 1987. At the time of the report more than 6000 such reports had been received, 80% concerning mucocutaneous reactions and most involving a generalised florid erythematous rash, often with pruritus. There were 178 reports of erythema multiforme, 30 of Stevens-Johnson syndrome, and 2 fatalities.
1. CSM. Fenbufen and mucocutaneous reactions. Current Problems 23 1988. Also available at: http://www.mhra.gov.uk/home/ idcplg?IdcService=GET_FILE&dDocName=CON2024430& RevisionSelectionMethod=LatestReleased (accessed 01/11/07)

Hypersensitivity.

See under Effects on the Lungs (above).

💊 Interactions

For interactions associated with NSAIDs. Use of fenbufen with aspirin may result in decreased serum concentrations of fenbufen and its metabolites.

💊 Pharmacokinetics

Fenbufen is absorbed from the gastrointestinal tract after oral use and peak plasma concentrations are reached in about 70 minutes. Fenbufen is over 99% bound to plasma proteins. It is metabolised in the liver to the active metabolites, biphenylacetic acid and 4-hydroxy-biphenylbutyric acid. Fenbufen and its metabolites are reported to have plasma half-lives of about 10 to 17 hours and are mainly eliminated as conjugates in the urine. Metabolites of fenbufen have been detected in breast milk in small amounts.

💊 Uses and Administration

Fenbufen, a propionic acid derivative, is an NSAID. It is given for the relief of pain and inflammation associated with musculoskeletal and joint disorders such as rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis in oral doses of 900 mg daily; the dose may be either 450 mg in the morning and evening or 300 mg in the morning with 600 mg in the evening.

💊 Preparations

BP 2008: Fenbufen Capsules; Fenbufen Tablets.

Proprietary Preparations

Austria: Lederfen†; Indon.: Cybufen; Irl.: Lederfen; Port.: Basifen; Reugast†; Thai.: Cepal; Cinopal†; Turk.: Cinopal; UK: Lederfen.
Published January 10, 2019.